Sampling Design

Terrestrial sampling options

In this file, the goal is to:

1. Examine the environmental coverage available within focal sites
2. Attempt to subdivide those focal sites into clusters for representative sampling

Sampling options

Figure 1. The full domain (light grey), available study sites (dark grey), and focal study sites (red).

Focal sites

Focal study sites have been selected on the basis of the following criteria:

• occur in the domain
• occur within a national park
• occur within 1 km of a road
• have a mean NDVI over the last year of > 0.2
• have a slope < 30 degrees
• are within an estimated hiking time of 2 hours from the road

Clustering

To better stratify our sampling, we’ll use k-means clustering to divide up the cells within the domain into clusters.

The variables going into the clustering are:

• Distance from water (including either rivers or wetlands, but not including the ocean)
• Drought (the number of droughts since 2000, quantified as the number SPEI values less than -1 since 2000)
• Soil Depth (from ISDASOIL, depth to bedrock, with a maximum values of 2 meters)
• Annual Mean Temperature
• Annual Precipitation
• Precipitation Seasonality (Coefficient of Variation)

Here I’m using k-means clustering to divide the data into 20 clusters. The number 20 was chosen entirely arbitrarily.

Visualizing our clusters

Geographic space

Figure 2. Spatial distribution of clusters. Polygons denote focal sampling locations.

Figure 3. Distribution of clusters across the domain (grey) and focal regions (blue).

Environmental space

Figure 4. Mean Annual Temperature vs. Mean Annual Precipitation. Colored dots represent clusters in the focal sites and grey areas represent the entire domain.

Figure 5. Precipitation Seasonality vs. Soil Depth. Colored dots represent clusters in the focal sites and grey areas represent the entire domain.

Figure 6. Distance to water vs. Drought. Colored dots represent clusters in the focal sites and grey areas represent the entire domain.

Vegetation Types

Figure 7. Distribution of biomes across the domain (grey) and focal regions (blue)

Clusters at a smaller spatial scale?

Include a leaflet plot here with focal sites broken into smaller polygons by cluster. Then color the polygons by cluster Intersect polygons with cluster polygons

Figure 8. Sampling options within parks. Park boundaries are denoted by black lines, sampling locations are colored by cluster.